1. Field of the Invention
The present invention relates to a shooting optical system for controlling a position of a lens unit constituting the shooting optical system to be a predetermined position in an optical axis direction to perform flange back adjustment. For instance, the present invention relates to the shooting optical system that is suitable for a video camera or a television camera.
2. Description of the Related Art
Conventionally, a zoom lens (shooting optical system) used in a broadcasting camera (TV camera) is provided with a macro mechanism that enables shooting a close object.
For instance, a lens unit included in a relay optical system (in a master lens unit) is moved to a macro shooting position based on a macro control signal from a macro control signal generation unit so that the macro shooting is performed.
In addition, many zoom lenses for a TV camera are provided with a flange back adjustment (tracking adjustment) mechanism for adjusting so that an image is formed on the image pickup element. This flange back adjustment is performed by moving the lens unit included in the relay optical system that is the same lens unit moved for the macro shooting based on a flange back control signal from a flange back control signal generation unit.
There is known a zoom lens that performs the above-mentioned operations by selecting each of the operations in accordance with operation of a selection switch (see Japanese Patent Application Laid-Open No. H10-153732).
As described above, the conventional zoom lens for a TV camera is provided with a flange back control signal (hereinafter, referred to as a flange back operating control signal) generation unit for flange back adjustment and the macro control signal generation unit for macro shooting.
Thus, a position of some of the lens units of the relay optical system is instructed by the flange back operating control signal when the flange back adjustment is performed, and instructed and controlled by the macro control signal when the macro shooting is performed.
The conventional zoom lens for a TV camera needs the flange back control signal generation unit, the macro control signal generation unit, and a switching unit or an adding unit for the signals. Therefore, the circuit scale is apt to increase. In addition, the flange back position is controlled by the flange back control signal, and hence a compensation circuit is also necessary for compensating for environmental variation such as temperature variation. In addition, a mechanical movement amount for the flange back adjustment is different for each type of the TV camera, and hence adjustment is necessary for each type thereof for matching an entire range of the flange back control signal generation unit with a moving range of a relay lens. Therefore, the circuit structure is apt to be complicated.